Magnetic brake for clock escapements



Feb. 22, 1966 R. s. WALTON 3,236,043

MAGNETIC BRAKE FOR CLOCK ESCAPEMENTS Filed April 16, 1963 I0 86 92 [00 FIG. I E 1 y 94 we 4 82 I V 96 [04 '2 v 7 76 v ,44 98 A, H 24* I8 e 34 32 22 58 24 26 |4 4e 42 1 20 48 30 y A Is 2s LI6 FIG. 3

INVENTOR RICHARD S. WALTON 24% a fa A TTORNE YJZ United States Patent 3,236,043 MAGNETIC BRAKE FOR CLOCK ESCAPEMENTS Richard S. Walton, Willow Street, Pa., assignor to Hamilton Watch Company, Lancaster, Pa., a corporation of Pennsylvania Filed Apr. 16, 1963, Ser. No. 273,426 11 Claims. (Cl. 58-145) This invention is directed to a magnetic brake structure for stopping the escapement of a watch, clock, or other timepiece, and more particularly is directed to a magnetic arrangement for locking the pallet of an engine hour meter.

Running time meters, and more particularly engine hour meters, are well known. These devices are useful for determining the actual elapsed running time of almost any type of equipment, and find particular utility in indicating the elapsed running time of an engine such as an automotive motor, a marine motor, and various types of electrical motors.

In prior constructions of the type to which the present invention is directed, the timepiece is spring-driven, runs when the power is on, and stops when the power is turned off; but only after the energy in the mainspring is dissipated. This continued running of the devices after removal of power introduces anerror into these prior systems. In the present invention this error is avoided by positively locking the clock escapement against further movement as soon as the electrical power is removed from the timer. Control of the running time is electrical and may be taken either from the input of the motor, if it is of the electrical type, or by suitable transducer arrangements from the motor output if of the internal combustion or gas turbine type. Alternatively, control may be derived from an internal combustion engine by connection to the low voltage supply for the ignition circuit.

In the past, several arrangements have been proposed for stopping a clock mechanism when power is removed from the system. Perhaps the most common is the type Where an arm comes down against the clock balance wheel and frictionally engages the balance wheel to stop the clock movement. The present invention, in providing a simplified magnetic device acting on the clock pal let, significantly improves over the moving arm and other known mechanisms in providing a simpler, more reliable brake involving no moving parts. The unit of the present invention is more durable and less subject to shock and insures accurate and positive actuation of the locking mechanism.

It is therefore one object of the present invention to provide an improved braking mechanism for timepieces.

Another object of the present invention is to provide an arrangement for locking the pallet of a timepiece.

Another object of the present invention is to provide an improved magnetic clock brake having no moving parts and one that is more reliable in operation and less subject to shock.

Another object of the invention is to provide an improved running time meter.

Another object of the invention is to provide an engine hour meter having improved accuracy.

These and further objects and advantages of the invention will become more apparent upon reference to the following specification, claims and appended drawings wherein:

FIGURE 1 is a partial cross section through a timepiece incorporating the novel brake constructed in accordance with the present invention;

FIGURE 2 is a plan view of a portion of the timepiece illustrated in FIGURE 1;

FIGURE 3 is an electrical circuit diagram for the timepiece of FIGURE 1; and

FIGURE 4 shows a modified brake arrangement constructed in accordance with the present invention.

Referring to the drawings, FIGURE 1 shows a portion of a timepiece generally indicated at 10 suitable for use as an engine hour meter. The timepiece is of the electrically rewound spring-driven type adapted to be energized from the ignition system of an automotive or marine engine. The timepiece comprises three parallel support plates 12, 14 and 16 separated by suitable spacers such as 18 and 20.

A balance staff 22 has its opposite ends rotatably journalled in upper plate 12 and lower plate 16 and carries a roller table 24 and a balance wheel 26. A hairspring 28 has one end connected to the balance staff 14 and its other end connected to a post 30 supported in lower plate 16.

Roller table 24 carries a jewel pin 32 which oscillates with the balance staff and engages the fork of a pallet lever 34 forming a part of the pallet generally indicated at 35. Pallet lever 34 is pivoted at 36 and the pallet arms 37 and 39 carry a pair of pallet jewels 38 and 40 which alternately engage the successive teeth of an escape wheel 42.

Escape wheel 42 is coupled to a more or less conventional clock train including fifth wheel 44, fourth wheel 46, center wheel 48 and third wheel 50. Center wheel 48 is coupled by a shaft 52 to an indicator hand 54 positioned over a dial plate 56 having suitable indicating indicia thereon.

The rotatable shaft 58 upon which third wheel is mounted is coupled by a one-way clutch in the form of a coil spring 60 passing through a siutable aperture in top plate 12 to a rotor 62 carrying weights 64 and 66. Rotor 62 is mounted on a shaft 68 having its lower end rotatably received in the upper end of a third wheel shaft 58 and its upper end rotatably received in the support bracket 70 mounted on the top plate 12. The opposite ends of coil spring 60 frictionally engage the underside of rotor 62 and the upper side of third wheel 50 so that for rotation of the rotor 62 in one direction energy is transmitted from the rotor through the spring or one-way clutch 60 to the third wheel 50 while, when the rotor rotates in the opposite direction, the clutch slips and no rotary motion is transmitted to third wheel 50.

The clock main spring 72 has one end connected to a post 74 on support plate 12 and its other end is connected to a pin 76 carried by rotor 62. One end of rotor 62 is provided with an electrical contact 78 adapted to engage a similar electrical contact 80 mounted on the end of armature 82 of a solenoid coil 84. Coil 84 is mounted in a frame 86 attached to top plate 12 and is provided with a core 88 adapted to engage the other end of armature 82 which armature is pivoted to frame 86 as indicated at 90. When the coil 84 is not energized, the end of armature 82 is biased against a stop 92 by a leaf spring 94.

The novel brake of the present invention generally indicated at 96 is mounted on top plate 12 and comprises an electromagnetic coil 98 surrounding a magnetic core 100 threadedly received through the top plate 12. Surrounding coil 98 is a ring or washer-shaped permanent magnet 102 magnetized along the axis of the ring or washer and secured in place by a frame 104 and a nut 106 threaded over the upper end of core 100. The lower end of the core 100 projects downwardly so that its lower end directly overlies one of the arms 37 or 39 of the pallet 35 in such a position that the magnetic flux from the lower end of core 100 causes the selected arm of the pallet to come to a position with its jewel 38 or 40 in engagement with a tooth of the escape wheel 42 to lock the escape wheel against rotation.

In operation, the unit is connected through an ignition switch indicated at 106 in FIGURE 3 to the power supply of an automotive or marine engine illustrated by the battery 108. When the ignition switch 106 is open and the unit is not energized, the arm of the pallet over which the core 100 is positioned, is locked in place in engagement with a tooth of the escape wheel 42 by the magnetic flux from the lower end of core 100 induced by the annular permanent magnet 102. On the other hand, when ignition switch 106 is closed, current is applied to coil 98 in such a direction as to oppose the field of permanent magnet 102 and of such magnitude as to create a flux equal to the flux of the permanent magnet. As a result, the net field in the core 100 is reduced to zero or substantially so, and the pallet is free to move under the influence of the rotating balance staff. A ten beat balance system may be utilized to assure self-starting of the balance system.

When the system is energized by the closure of ignition switch 106, main spring 72 acts on rotor 62 to cause the rotor to rotate in a clockwise direction in FIGURE 2 so as to cause the contact 78 to approach contact 80. When contacts 78 and 80 close, the circuit is completed through solenoid coil 84 energizing this solenoid and causing the armature 82 to move over into engagement with core 88. The previous clockwise movement of the rotor 62 is transmitted through the one-way clutch to the third wheel 50 causing rotation of the train and movement of the indicating hand 54.

Energization of the armature 82 by coil 84 causes the armature to physically impart a counterclockwise rotation to rotor 62 acting to rewind main spring 72. During this counterclockwise rotation of the rotor 62, clutch 60 slips and no rotation is imparted to the clock train. When the end of armature 82 engages the core 88, the core acts as a stop preventing any further movement of the armature. However, the inertial forces imparted by the armature to the rotor 66 cause the rotor to continue to move in the counterclockwise direction in FIGURE 2 further winding the main spring until the inertia of the rotor is overcome by the main spring and the rotor stops in the approximate position illustrated in FIGURE 2. The continued movement of the rotor when the armature stops causes the contacts 78 and 80 to part thus breaking the circuit to solenoid coil 84 and the armature 82 returns under the influence of spring 94 to the position illustrated in FIG- URE 2. Thus, during operation the spring-driven clock structure indicates elapsed energized time under the influence of escape pallet 35 while the main spring is periodically electrically rewound from the electrical power supply source of the unit. Locking of the escape pallet by the magnetic brake upon the opening of ignition switch 106 stops the entire unit.

FIGURE 4 shows a modified embodiment of the novel brake mechanism of the present invention with corresponding parts bearing like reference numerals. In this embodiment, a permanent magnet 110 is threadedly received in top plate 12 and projects downwardly adjacent one arm of the pallet arm 39. An additional support plate 112 is provided and suitably secured to this plate and projecting upwardly adjacent the end of permanent magnet 110 is a core 114. Surrounding the end of core 114 and similarly secured to the plate 112 is an electromagnetic coil 116. Contrary to the embodiment of FIG- URE 1, wherein the vertical axis of core intersects the end of pallet arm 39 as indicated by the cross 100 in FIGURE 2, the vertical axes of permanent magnet and core 114 are slightly ofifset from each other and from pallet arm 39 as indicated by' the crosses 110 and 114 in FIGURE 2. The operation of the embodiment of FIG- URE 4 is similar to that of FIGURE 1 in that when the ignition switch 106 is open the pallet arm 39 is attracted by the magnetic flux from core 110 towards the escape wheel 42 such that the pallet jewel 38 is in locking engagement with one of the teeth of the escape wheel.

However, in FIGURE 4 when the ignition switch 106 is closed, energy is supplied to coil 116 in such away as to magnetize the end of core 114 closest to the permanent magnet 110 with an opposite polarity to that of the closest end of the permanent magnet. Rather than being neutralized, the flux path is redirected from its path of least resistance (to the pallet arm 39) so that it now passes to the core 114 with most of the flux bypassing pallet arm 39 thus leaving the pallet arm free to swing. As an alternative to that shown the core 114 and coil'116 may be mounted on plate 12 so that the core lies parallel with magnet 110, preferably on a side remote from the escape wheel and pallet. As in the arrangement shown the inner end of the core should be closely adjacent the inner end of magnet 110 to redirect the magnet flux.

In order to operate satisfactorily, the novel magnetic brake mechanisms of the present invention should be employed with a pallet made of steel or other good magnetic material. Similarly, while not absolutely essential, it is preferred that a non-magnetic escape wheel be utilized. While the locking magnetic field has been shown in both embodiments as located to draw the pallet arm 39 and hence pallet jewel 38 into engagement with the teeth of escape wheel 42, it is apparent that the magnetic elements may, if desired, be located so as to pull arm 39 away from the periphery of escape wheel 42. In this alternative arrangement, when the arm 39 is pulled away from the escape wheel, the pallet 35 pivots about 36 so that the pallet jewel 40 on arm 37 is brought into locking engagement with the teeth of the escape wheel 42.

It is apparent from the above that the present invention provides a novel magnetic braking system for timepiece movements employing an escapement made of magnetic material. The direction of magnetic flux used to brake the escapement mechanism is perpendicular to the pallet and escape wheel and is thus limited to a small portion of the movement and has a minimum efiect on the adjacent moving parts of the timepiece. The brake is of relatively simple construction which may be economically manufactured and requires no moving parts. It is more durable and more reliable in operation than prior known systems and is substantially insensitive to shock.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A brake for timepieces having a movable magnetizable pallet adapted to engage the teeth of an escape Wheel, comprising a permanent magnet adjacent said pallet creating a flux acting to move said pallet into locking engagement with said escape wheel, and an electromagnet adjacent said permanent magnet which when energized nullifies the effect of said permanent magnet flux on said pallet to unlock said pallet.

2. A brake according to claim 1 wherein said electromagnet creates a flux coincident with and opposite to said permanent magnet flux to reduce to a minimum the net flux acting on said pallet.

3. A brake according to claim 1 wherein said electromagnet when energized creates a path of less resistance for said permanent magnet flux so as to direct said permanent magnet flux away from said pallet to unlock said pallet.

4. A timepiece comprising a mainspring, a gear train coupling said mainspring to indicating means, an escape wheel coupled to said gear train, a magnetizable pallet coupled to said escape wheel for controlling the energy delivered to said indicating means from said mainspring,

permanent magnet means for locking said pallet, and electromagnetic means for unlocking said pallet.

5. A timepiece comprising a mainspring, means for winding said mainspring, a gear train coupling said mainspring to indicating means, an escape wheel coupled to said gear train, an oscillating balance system driving a magnetizable pallet, said pallet acting through said escape wheel to control the energy delivered to said indicating means from said hairspring, a permanent magnet adjacent said pallet creating a flux acting to move said pallet into locking engagement with said escape wheel, and an electromagnet said permanent magnet which when energized nullifies the efiect of said permanent magnet flux on said pallet to unlock said pallet.

6. A timepiece according to claim 5 wherein said mainspring is electrically rewound.

7. A running time meter comprising a mainspring, electromagnetic means for periodically rewinding said mainspring, means for coupling said electromagnetic rewind means to an electrical source, a gear train coupling said mainspring to indicating means, an escape wheel coupled to said gear train, an oscillating balance system driving a magnetizable pallet, said pallet acting through said escape wheel to control the energy delivered to said indicating means from said hairspring, a permanent magnet adjacent said pallet creating a flux acting to move said pallet into locking engagement with said escape wheel, an electromagnet adjacent said permanent magnet which when energized nullifies the affect of said permanent magnet flux on said pallet to unlock said pallet, and means coupling said electromagnet to an electrical source to be metered.

8. An engine hour meter comprising a mainspring, electromagnetic means for periodically rewinding said mainspring, means for coupling said electromagnetic rewind means to an electrical source, a gear train coupling said mainspring to indicating means, an escape wheel coupled to said gear train, an oscillating balance system driving a magnetizable pallet, said pallet acting through said escape wheel to control the energy delivered to said indicating means from said mainspring, a permanent magnet adjacent said pallet creating a flux acting to move said pallet into locking engagement with said escape wheel, an electromagnet adjacent said permanent magnet which when energized nullifies the effect of said permanent magnet flux on said pallet to unlock said pallet, and means coupling said electromagnet through the ignition switch of a vehicle motor to the motor electrical power supply.

9. A meter according to claim 8 wherein said pallet forms part of an anchor escapement and said escape wheel is nonmagnetic.

'10. A meter according to claim 9 wherein said permanent magnet is annular in shape and surrounds an elongated core extending perpendicular to the plane of oscillation of said pallet and terminating adjacent one arm of the pallet, said electromagnet also surrounding said core.

11. A meter according to claim 9 wherein said permanent magnet is of elongated shape and is positioned on the opposite side of the plane of oscillation of said pallet from said electromagnet, said el-ectromagnet surrounding an elongated core having one end spaced from but adjacent an end of said permanent magnet, the longitudinal axes of said permanent magnet and said core being perpendicular to said plane of oscillation but laterally offset from said pallet with the axis of said core furthest from the pallet.

References Cited by the Examiner UNITED STATES PATENTS 2,574,583 11/1951 Nallinger 58-146 2,669,089 2/ 1954 Straumann 58- 121 2,978,863 4/ 1961 Strobel 58 3,058,356 10/1962: Welch et al. 741.5

FOREIGN PATENTS 128,074 10/ 1928' Switzerland.

OTHER REFERENCES German application (Junghans) published November 1962, No. 1,140,148.

LEO SMI-LOW, Primary Examiner. 

1. A BRAKE FOR TIMEPIECES HAVING A MOVABLE MAGNETIZABLE PALLET ADAPTED TO ENGAGE THE TEETH OF AN ESCAPE WHEEL, COMPRISING A PERMANENT MAGNET ADJACENT SAID PALLAT CREATING A FLUX ACTING TO MOVE SAID PALLET INTO LOCKING ENGAGEMENT WITH SAID ESCAPE WHEEL, AND AN ELECTROMAGNET ADJACENT SAID PERMANENT MANGT WHICH WHEN ENERGIZED NULLIFIES THE EFFECT OF SAID PERMANENT MAGNET FLUX ON SAID PALLET TO UNLOCK SAID PALET. 